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RE: "their size is the equivilent of the size of the opening when a standard door is open one inch."

Posted by David Aiken (A) on May 10, 2009 at 13:43:11

In Reply to: RE: "their size is the equivilent of the size of the opening when a standard door is open one inch." posted by Ethan Winer on May 10, 2009 at 09:44:40:

Well, we believe size is a given and there are extremely compelling reasons for thinking so. A passive acoustic treatment can only act on the sound which actually falls on it, and the most it can absorb is all of the sound that falls on it. The only way we can get reduce size without compromising performance is by increasing effectiveness and there's always going to be a finite limit to what we can do there. Broadband absorption is the ideal for a couple of reasons to do with both impact on the sound we hear and also the fact that such treatments can be used in any room or space so that makes them a commercially more viable product for manufacture but they can never be more efficient than 1 Sabin of absorption per square foot of surface area. We can get more effective absorption than that from a device like a Helmholtz resonator but then we lose broadband performance and achieve maximum efficiency over an extremely narrow bandwidth of a couple of Hz at most.

And the Cathedral Panels are a passive acoustic treatment in the same way that my RealTrap panels are—they can only work on the sound falling on them. Their area is 11" x 16" which is 182 square inches so at most you could get 1.25 Sabins of absorption from a panel. Using the 1" door opening statement as an indication of how effective they're claimed to be, we're talking around .4 of a Sabin over an unspecified frequency range. If they're actually getting that at the below 40 Hz frequencies indicated by their plots they're doing extremely well but it's quite a trick to do that and have no effect above 40 Hz. That would mean that they aren't broadband in operation and if they're not broadband they're not going to be an effective treatment on their own because if we're going to treat, we need to treat over a wider bandwidth than just up to 40 Hz because modal problems occur over a wider bandwidth than that in every room.

The problem with the claims made for the Cathedral Panels is that if the claims are true and they are effective at controlling standing wave behaviour at frequencies up to 200 Hz, then the plots don't show what's going on because they should show significant benefit above 40 Hz, and if the plots do show what is actually going on, then the claims can't be true because the plots aren't showing significant benefit above 40 Hz even though the untreated room plot is showing standing wave behaviour there, actually more standing wave problems there than below 40 Hz. One assumes they show the best test data they have because you want to present the product in the best light so even if we accept the plots at face value, which I don't, things simply don't add up. The plots are showing something different from the performance claims being made, something that fails to support those claims.




David Aiken

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